The present disclosure relates to electric motor-driven compressors such as used for fuel cells.
Air compressors can be used to increase the efficiency of a fuel cell by providing compressed air to the cathode side of the fuel cell. A two-stage compressor may be used in some applications requiring a higher pressure than achievable in a single compressor stage. In a two-stage compressor, a low-pressure compressor wheel is provided on a shaft, and a high-pressure compressor wheel is provided on the same shaft. The shaft is driven by an electric motor so that the compressor wheels are rotated, and air enters the low-pressure compressor wheel and is compressed to a first pressure. The compressed air is then passed on to the high-pressure wheel for a further increase in pressure. The air from the high-pressure compressor wheel is then delivered to the fuel cell to promote the fuel cell reaction.
The electric motor used in a compressor for a fuel cell is typically a high-speed, high-output motor that generates a significant amount of heat. It is generally desirable to minimize the heat transfer between the motor and the air being compressed in the compressor, and the heat transfer between the motor and the bearings for the compressor shaft.